solar can heater project

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Project 2: Solar Powered Water Heater Jacob Aucoin Nicholas Chua Dijon Hill Harold Nero Due Date: 10/24/2014

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Page 1: Solar Can Heater Project

Project 2:

Solar Powered Water Heater

Jacob Aucoin

Nicholas Chua

Dijon Hill

Harold Nero

Due Date: 10/24/2014

Page 2: Solar Can Heater Project

ABSTRACT

This report is about the successful development of a prototype hot water heater using beverage cans and

other materials within the range of a budget. In order to remain in budget, research on possible materials that

can be used to build this prototype cost effectively was necessary. After completing our search, we narrowed

down the best options for the project before proceeding to the building phase. The idea was to make the exterior

box as cheap as possible so we could invest into the performance of the actual system that is within the box. We

discovered hiccups along the way as we began to build this solar powered water heater and wasted no time in

correcting those issues. After everything in the unit was in place, we tested the flow rate and temperature

change various times to ensure our efforts were not in vain. When testing gave back positive results we were

confident that we made a unit that gave us the results necessary to pass the in class testing while managing to

remain within budget

INTRODUCTION

Of the numerous problems that this project brought to the table, we managed to face each one head on

and conquer them one by one. One problem, that remained ever-present, was not exceeding our budget of $75.

The first problem was determining a reasonably sized prototype even though we were given maximum

dimensions of 4ft x 8ft x 1ft. For our purposes, we quickly came to the conclusion of simply halving the

maximum dimensions given to us by our instructor at the height, length, and depth of 2ft x 4ft x 0.5ft. Although

briefly stated in the previous section, part of our analysis for this project was to determine the materials we

would use to build our prototype. We determined many options for different parts of the project to be very

effective but we soon found out that the best route would not always keep us below budget. Keeping the budget

in mind made the selection of materials easy because the majority of the options out there were more than likely

going to take us over our predetermined $75 budget.

We already knew that this budget included the value of cans and all parts, including “found” and

“repurposed” items. Later on in our analysis, the cost of labor and overhead would also have to be considered.

The design is constrained by the flow rate and temperature increase. The minimum flow rate is ½ gallons per

minute and the minimum change in temperature, from entrance to exit, must increase 5 to 12 degrees. Part of

our analysis was realizing that the prototype was mainly constrained by the cost, so the goal was to build a

sufficiently large box that could be cheaply sealed to increase convection within the box heated by black cans.

Ideally, we wanted water touching aluminum for better conduction, but the added cost of sealing cans water

tight or running water through faster to avoid leaking was more trouble than it was worth. Through further

thought, we realized that this would be corrected with the particular type of hosing that was used. So instead, we

relied on the convection within the box to help transfer the heat threw a ½” plastic tube running through rows of

black cans. This added reliability and helped maintain the required flow rate. Our design has a leak-free tube

running through rows of cans. What sets our prototype apart, is the well-sealed box and large number of cans.

An outline of our design will be seen at the end of the report.

EQUIPMENT

For testing we used two five gallon buckets, a thermometer, and a stopwatch. Our box was built out of a

plywood (2ft x 4ft x 0.25in), wood (1x6x12) that was cut down to build the four sides of the box and nailed

together, and sealed with saran wrap after the placement of our system within the box. The cans were lined up

in rows with a ½” vinyl tube running through the cans, all cans were tapped with HVAC Foil Tape and they

Page 3: Solar Can Heater Project

were spray painted black to absorb the maximum amount of sunlight. Other equipment that was used along the

way included: nails, aluminum foil, reflective tape, a hose connector, package tape, and a funnel.

PROCEDURE

In constructing this unit, we brought all of our materials in front of us to ensure that everything we

needed to make this project would be within our grasp. The device was left good sun light for about 20 minutes

to reach its maximum temperature. The temperature of the prepared water was measured and recorded as 71

degrees Fahrenheit. Water was then poured into the inlet of the tube and when water began flowing out at a

steady state, the stopwatch was started until ½ gallons had flowed through steadily. The change in temperature,

dT, over the change in time gave us a result of ½ gallon per min flow rate, shown as dV in later figures where

you can follow the calculations for the power absorbed by the water. The gal per min flow rate was changed to

gal per second then multiplied by the density of water, rho, in kg per gallon giving the mass flow rate, dm, in kg

per second. (Cengel & Boles, 2011) The mass flow rate was then multiplied by the specific heat of water, Cp, at

71 degrees Fahrenheit and the temperature change in Kelvin giving the power in Watts absorbed by the water.

(Cengel & Boles, 2011) The solar power was assumed to be 500W/m², which after multiplying by the area of

cans, gives the solar power supplied to the prototype. Water is poured through, while flow rate and temperature

are measured at the outlet. The energy being absorbed by the water is calculated from the temperature change

and flow rate. If compared to the energy available from the sun, our design can be evaluated by its efficiency.

The prototype can also be evaluated by its manufacturing cost per unit.

DATA/RESULTS

The manufacturing cost came to $68.29. With a 20% margin, the retail price would be $81.95. After

1000 units a profit of $1660.00 is expected. The overhead and equipment cost are negligible. This is because it

is so easy to assemble and could be done in any workshop or garage with a saw and drill. The 1 hour of

assembly is conservative and could range more between 30-45 minutes. All the costs are shown in , the

manufacturing cost, retail price, & potential cost and profits for 1000 units are shown in a later figure. A plot of

the cost is also shown in later figures.

The solar powered water heater worked as expected and the temperature rose by 31 degrees, 25 degrees

more than the required minimum. The efficiency of a device with an increase of 5 degrees is 87.3% Therefore

there is no reason for improvements, but more testing is needed. The initial temperature of the mass of

aluminum is causing such a large temperature change that the results show that a steady state was never

reached. If it reached steady state, the efficiency would be 641%. In additional testing an initial hot temperature

for calculating the energy lost by the aluminum or longer testing is required to reach the temperature at which

the solar energy balance the energy removed by the water. The power supplied by the sun is 500W/m². The

power removed by the water is calculated from the specific heat at constant

pressure. (Cengel & Boles, 2011) For the more conservative and realistic estimate

with a temperature gain of 5 degrees Fahrenheit see later figures. These figures show not only the efficiency’s,

but also the cost savings and payback period and various other important data.

CONCLUSION

The prototype, as designed now, could save someone money. Although it would take a long time to

make any profits and a lot of man hours to create the amount of units necessary to even make a profit if we

viewed our idea in retrospect to a small startup company. At the conservative 5 degree Fahrenheit increase it

Page 4: Solar Can Heater Project

could possibly pay for itself in 8 months if a group of brave individuals were willing to go through with this

idea of being economically conscious. Tests of our unit conclude that our choice was highly effective in getting

the end results but calculations seem to show that it is not highly profitable in the long run. Our analysis works

in the since of making only 1 unit and using that same unit over a long period of time (This is how we can get a

large return on our investment). However, the opposite becomes true when we are making several units that

need to be distributed for only a 20% rate of profit. In order to get all of our data to be perfectly unified across

the board, many more tests would have to be conducted to rule out all possible scenarios. This product can be

improved by taking out materials that increase the amount of heat coming to our system and make the unit as

basic as possible (which would also take away from the amount of time needed in making the unit). In closing,

one possible theory that was missing from the theory of this project was the concept of the transfer of heat

between mediums. This is because our heat source that we get from the sun must pass into our box via radiation,

once the box is heated then that heat must in turn heat the cans, and once the cans are heated then the heat in the

cans must be high enough (which it was) to heat the water in the hose. In other words, further calculations could

have been done to show the passage of heat through all of the mediums that made up our unit.

Page 5: Solar Can Heater Project

Date Account Description Hotel Subtotal 8% Tax 9% Tax 9.75% Tax Misc. Total

10/8/2014 N/A Vinyl Tubing (2) N/A $14.98 $1.20 $16.18

10/9/2014 N/A HVAC Foil Tape N/A $7.98 $0.64 $8.62

10/9/2014 N/A Nails N/A $1.50 $0.14 $1.64

10/9/2014 N/A Aluminum Foil (2) N/A $4.00 $0.36 $4.36

10/9/2014 N/A Black Paint N/A $1.92 $0.15 $2.07

10/9/2014 N/A Wood 1x6x12 N/A $7.48 $0.73 $8.21

10/9/2014 N/A Reflective Tape N/A $3.25 $0.32 $3.57

10/9/2014 N/A Saran Wrap N/A $2.27 $0.22 $2.49

10/9/2014 N/A Package Tape N/A $1.00 $0.09 $1.09

10/9/2014 N/A Connector N/A $2.99 $0.24 $3.23

10/9/2014 N/A Wood 0.25x2x4 N/A $8.52 $0.77 $9.29

10/9/2014 N/A Funnel N/A $4.37 $0.39 $4.76

10/9/2014 N/A Aluminum Cans N/A $2.78 $2.78

$0.00

$0.00

$0.00

$0.00

$0.00

Total $0.00 $63.04 $2.23 $0.50 $2.52 $0.00 $68.29

SUBTOTAL $68.29

APPROVED: NOTES: ADVANCES $0.00

TOTAL $68.29

APPENDIX

Figure 1: Table of Material Costs

Figure 2: Plot of Material Cost

Page 6: Solar Can Heater Project

Figure 3: Break Even Analysis

Figure 4: Price Estimates

BREAK-EVEN ANALYSIS

Break Even Units:

Retail Price per Unit:

Expected Unit Sales:

Total Variable Unit Costs:

Total Fixed Costs (Overhead):

You will be making profit after 878.48 units.

81,950.00

-7,902.00

-6,536.00

-5,170.00

-3,804.00

-2,438.00

-1,072.00

294.00

1,660.00

8,195.00

16,390.00

24,585.00

32,780.00

40,975.00

49,170.00

57,365.00

65,560.00

73,755.00

66,632.00

73,461.00

80,290.00

52,974.00

68,290.00

59,803.00

6,829.00

13,658.00

20,487.00

27,316.00

34,145.00

40,974.00

47,803.00

54,632.00

61,461.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

12,000.00

1,000

300

878.48

Fixed Cost Variable Cost Total Cost

400

500

600

700

800

900

18,829.00

25,658.00

32,487.00

39,316.00

46,145.00

12,000.00

68.29

1,000

81.95

Revenue ProfitUnits

100

200

-10,634.00

-9,268.00

0

50000

100000

150000

200000

250000

300000

Re

ven

ue

Units

Fixed Cost

Variable Cost

Total Cost

Revenue

Page 7: Solar Can Heater Project

Figure 5: Energy & Efficiency

SUN:L, m W, m A, m^2 min, W/m^2 max, W/m^2 P_min, W P_max, W P_solar, W

0.6 1.2 0.7 500 700 348.7 488.2 418.5

WATER:dV, gal/min dV, gal/s rho, kg/gal dm, kg/s Cp, J/kg-K dT,F dT,K P_water, W

0.5 8.33E-03 3.77 0.0315 4.18E+03 5 2.8 365.2

Energy Saved:η 87.3% Energy, kWh/day 2.9

Avg US Elec.($/kWh) 0.13$

Yearly Savings 136.81$

Monthly Savings 11.40$

Payback (months) 7.8

EFFICIENCY:

Figure 6: Energy and Efficiency

SUN:L, m W, m A, m^2 min, W/m^2 max, W/m^2 P_min, W P_max, W P_solar, W

0.6 1.2 0.7 500 700 348.7 488.2 418.5

WATER:dV, gal/min dV, gal/s rho, kg/gal dm, kg/s Cp, J/kg-K dT,F dT,K P_water, W

0.5 8.33E-03 3.77 0.0315 4.18E+03 31 17.2 2264.1

Energy Saved:η 541.1% Energy, kWh/day 18.1

Avg US Elec.($/kWh) 0.13$

Yearly Savings 848.21$

Monthly Savings 70.68$

Payback (months) 1.3

EFFICIENCY:

Page 8: Solar Can Heater Project

Figure 7: Hand Written Calculations

Page 9: Solar Can Heater Project

Figure 8: Hand Written Calculations Continued

Page 10: Solar Can Heater Project

Figure 9: Hand Written Calculations Continued

Page 11: Solar Can Heater Project

Figure 10: Receipts

Page 12: Solar Can Heater Project

Figure 11: Receipts Continued

Page 13: Solar Can Heater Project

Figure 12: Receipts Continued

Page 14: Solar Can Heater Project

Figure 13: Dimensional Design and Parts

Page 15: Solar Can Heater Project

Figure 14: Dimensional Design and Parts Continued

References

Cengel, Y. A., & Boles, M. A. (2011). Thermodynamics: An Engineering Approach (7th ed.). New York, NY, US: McGraw-

Hill. Retrieved 10 22, 2014